You have to enable the payment gateway feature in your Navotar account first. For this, contact firstname.lastname@example.org and subscribe to the feature.
Currently, Navotar supports Cardknox, Authorize.net, CardConnect and PayPal as payment gateways. You may subscribe to one of these gateways and contact email@example.com to have the feature set up for your account.
If you wish to integrate your account with a payment gateway of your choice, it is still possible but you will have to contact a Navotar representative before moving forward.